1. Technical Field of the Invention
The present invention relates to a plastic working method and plastic working system, in the working line of which a plurality of plastic working devices are arranged and a workpiece can be smoothly supplied to the working devices and a high speed operation can be executed.
2. Description of the Related Art
In a conventional plastic working device, for example, a conventional press device is incorporated into a press working line to which a coil material, which is a workpiece, is supplied so that it can be worked by press working, the coil material is delivered from an uncoiler which holds and uncoils the coil material and the coil material is made to pass through a leveler which straightens the coil material and also made to pass through a section, in which a loop (slack or loosening) is generated, and the coil material is sent to a press device through an intermittently feeding mechanism so that the coil material can be subjected to press working.
In this case, the supply operation of coil material to the press device will be done intermittent to the press operation that repeats the movement and the stop. Which results in the coil material vibrating and flapping in some cases.
When the coil material flap as described above, not only the intermittently feeding mechanism receives an excessively heavy load, but also the coil material is bent and damaged which results in the material being erroneously fed. In order to reduce the flapping of the coil material, the following method is employed. For example, a pair of feed rollers having a servo motor are arranged before the intermittently feeding mechanism so that it can be used as a loop controller. The coil material is supplied to the intermittently feeding mechanism while an appropriate loop is being formed by these feed rollers.
Due to the above structure, the loop size of the coil material is detected. By this detection signal, a servo motor speed is controlled so as to control an amount of feed of the coil material. By this constitution, the coil material can be supplied to the intermittently feeding mechanism while an appropriate loop is being maintained. Therefore, flapping of the coil material can be minimized and the operation can be executed at high speed.
However, while the material to be processed is diversified, for instance, the size of the allowed loop is different for the difference of board thickness. Therefore, to form an appropriate loop, loop controller's installation position becomes a problem.
In order to solve the above problems, more flexibly, to supply the material in the high quality, JP-A-2004-142876 proposes the following coil material supply device. The coil material supply device for supplying a coil material to an intermittently feed device incorporated into a press device comprises: a coil material supply portion; a position sensor, which is arranged on the downstream side of this coil material supply portion, for detecting an amount of loop of the coil material; a control unit for controlling an amount of feed of the coil material executed by a feed roller when a servo motor is controlled by a signal sent from the position sensor; and a stand for holding the coil supply portion, the attaching angle of which can be changed so that a supply angle of the coil material can be changed in accordance with a condition of supplying the coil material.
However, JP-A-2004-142876 discloses a coil material supply device applied to a press working line in which press working is executed by one press device. Accordingly, improvement in production capacity is limited. Therefore, a press working line is proposed in which a plurality of press devices are arranged in series to each other and synchronously operated by a predetermined phase difference so as to enhance productivity.
However, this coil material supply device is disadvantageous in that even when the plurality of press devices are arranged in series to each other, a feed mechanism incorporated into each press device is intermittently operated. Therefore, due to the flapping generated in a workpiece located between the press devices, erroneous feeding is induced in the press device arranged before and after the coil material supply device. Accordingly, it is only possible to execute a low speed synchronous operation. Therefore, it is difficult to enhance productivity.
On the other hand, when the same working is executed not by an intermittent type device, but by a continuous feed type device, the occurrence of flapping of a workpiece can be reduced. However, the repetitive accuracy of the continuous feed type device is lower than that of the intermittent type device. Further, when the operation speed is increased, there is a fault that the decrease in accuracy repeatedly becomes remarkable.